In general, streetlamps are lighting apparatuses that are installed along the road for safe road traffic, and various types of streetlamps are used according to the installation positions thereof, such as an expressway, main roads in the city, roads in a business section, and roads in a residence section.
The lighting apparatus includes a lamp housing that has a reflecting plate formed on the inner surface thereof and is mounted to a lamp post and a light source that is provided in the lamp housing to emit light.
The lamp posts are classified into various types, such as a highway type in which a lamp is attached to the end of a curved portion of a lamp post, a bracket type in which a lamp is attached to a branch horizontally extending a lamp post, and a column capital type in which a lamp is attached to the top of a lamp post.
In addition, a general lamp, such as a high-pressure sodium, metal halide, or a mercury vapor, is used as the light source.
The streetlamp emits predetermined color light, such as white, yellow, or blue light, according to the type of light source provided therein. Of course, the color of light emitted from the streetlamp may be selected according to, power efficiency, light intensity, or the surrounding environment.
Meanwhile, the streetlamp is designed to have a shape capable of most effectively illuminating the road with a suitable light distribution type when it is installed on the road. As shown in FIG. 1, first to five light distribution types are generally used to illuminate the road. Except for some special cases, the second to fourth light distribution types can effectively illuminate most of the road.
In the streetlamp according to the related art, the reflection angle of a reflecting plate provided in a lamp housing is adjusted to illuminate the road with a suitable light distribution type in the road light design.
However, it is difficult for the user to arbitrarily adjust the brightness and diffusion range of light emitted from various lamps, such as a high-pressure mercury lamp, a fluorescent lamp, and a sodium lamp, used as a light source in the streetlamp according to the related art, since the brightness and the diffusion range are fixed during the manufacture of the lamps, and the lamps have a very short life span and a large amount of power consumption.
In order to solve these problems, in recent years, a lighting apparatus using light emitting diodes (LEDs) as a light source has been proposed. In addition, with the development of technique, light emitting diodes with a small amount of power consumption and high brightness have been developed and come into widespread use.
As shown in FIG. 2, in the lighting apparatus using the light emitting diodes, generally, a plurality of light emitting diode modules 10a are mounted to the lower surface of an upper plate 11 of the lamp housing member 10, and a reflecting plate 10b is provided on the inner surface of a side portion 12 of the lamp housing member 10. The light emitting diode modules 10a and the reflecting plate 10b are used to illustrate the road.
In the lighting apparatus using the light emitting diodes, the plurality of light emitting diode modules 10a are mounted to the lower surface of an upper plate 11 in order to ensure a cut-off-angle at which pedestrians or drivers cannot directly view the light emitting diode modules within a predetermined angle range.
In a lighting apparatus including the light emitting diodes as well as the lighting apparatus using the light emitting diodes, when light from light source is directly emitted to the pedestrians or drivers, light is likely to hinder the walking of the pedestrians or the driving of the drivers, which may cause traffic accidents. Therefore, it is essential to ensure the cut-off-angle.
The light emitting diode has a substantially permanent life span, as compared to the lamps according to the related art, and the brightness of light emitted from the light emitting diodes is determined by a combination of the light emitting diodes. However, when light distribution is formed by the reflecting plate, a light distribution area is small, and brightness is low. In addition, there are limitations in forming sufficient light distribution to effectively illuminate the road surface, that is, in forming the first to fifth light distribution types.
Further, since it is difficult to effectively dissipate heat generated from a plurality of light emitting diodes, emission efficiency is lowered due to heat, which results in the damage of parts.
Therefore, the lighting apparatus using the light emitting diodes depends on only the reflecting plate to provide desired brightness except for the ideal arrangement of the light emitting diodes during manufacture. As a result, the lighting apparatus using the light emitting diodes is ineffective to illuminate the road, and is not used in the wide range.
Further, a lighting apparatus using light emitting diodes shown in FIG. 3 has been proposed in which a plurality of light emitting diode modules la are mounted to a V-shaped lamp mounting frame 1 at predetermined intervals.
The lighting apparatus using the light emitting diodes can adjust light distribution and a light distribution area by adjusting the angle of the lamp mounting frame 1. However, there are limitations in the adjustment of the angle, and since the light emitting diode modules 1a are exposed to the outside, light emitted from the light emitting diode modules is directly emitted to the eye of the pedestrian or the driver, which may interfere with safe walking or driving due to glare.